1. Field of the Invention
This invention relates to the field of electrochemistry.
2. Description of the Prior Art
Hydrogen atoms can be absorbed into metals such as steels due to corrosion or during pickling, plating, or welding. During these processes, hydrogen may enter the metallic lattice interstitially and permeate throughout the metal. As a result, the ductility of the metal can be reduced greatly, a phenomena known as hydrogen embrittlement.
The amount of hydrogen required to cause embrittlement of high strength steels is in the parts per million range. Vacuum fusion techniques are known for determining the hydrogen content of metals, but these techniques are expensive and require destruction of the part being analyzed. A non-destructive technique based upon measuring the permeation of hydrogen through the metal has been proposed (D. A. Berman, W. Beck, and J. J. DeLuccia in "Hydrogen in Metals", I. M. Bernstein and W. W. Thompson, Editors, ASM (1974), p. 595). According to the Berman et al technique, a "barnacle cell" is attached to the metal. The barnacle cell is the anodic side of a hydrogen permeation apparatus and it utilizes a large non-polarizing electrode to oxidize hydrogen atoms that are electrochemically induced out of the metal. The resulting hydrogen oxidation current is then used to calculate the concentration of hydrogen in the metal part from Faraday's law and from known diffusion equations.
The use of barnacle cells to measure hydrogen in metal parts requires that cup-like cells full of electrolyte be positioned on the metal surface. Additionally, the hydrogen oxidation current must be accurately measured. Until the present invention, such problems have prevented the practical use of hydrogen permeation to measure the hydrogen concentration in metals.